auth2.c - platform/external/openssh - Gitiles

 /*
  * Copyright (c) 2000 Markus Friedl.  All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  *
  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */

 #include "includes.h"
 RCSID("$OpenBSD: auth2.c,v 1.89 2002/03/19 14:27:39 markus Exp $");

 #include <openssl/evp.h>

 #include "ssh2.h"
 #include "xmalloc.h"
 #include "rsa.h"
 #include "sshpty.h"
 #include "packet.h"
 #include "buffer.h"
 #include "log.h"
 #include "servconf.h"
 #include "compat.h"
 #include "channels.h"
 #include "bufaux.h"
 #include "auth.h"
 #include "session.h"
 #include "dispatch.h"
 #include "key.h"
 #include "cipher.h"
 #include "kex.h"
 #include "pathnames.h"
 #include "uidswap.h"
 #include "auth-options.h"
 #include "hostfile.h"
 #include "canohost.h"
 #include "match.h"
 #include "monitor_wrap.h"

 /* import */
 extern ServerOptions options;
 extern u_char *session_id2;
 extern int session_id2_len;

 Authctxt *x_authctxt = NULL;
 static int one = 1;

 typedef struct Authmethod Authmethod;
 struct Authmethod {
 	char	*name;
 	int	(*userauth)(Authctxt *authctxt);
 	int	*enabled;
 };

 /* protocol */

 static void input_service_request(int, u_int32_t, void *);
 static void input_userauth_request(int, u_int32_t, void *);

 /* helper */
 static Authmethod *authmethod_lookup(const char *);
 static char *authmethods_get(void);
 int user_key_allowed(struct passwd *, Key *);
 int hostbased_key_allowed(struct passwd *, const char *, char *, Key *);

 /* auth */
 static void userauth_banner(void);
 static int userauth_none(Authctxt *);
 static int userauth_passwd(Authctxt *);
 static int userauth_pubkey(Authctxt *);
 static int userauth_hostbased(Authctxt *);
 static int userauth_kbdint(Authctxt *);

 Authmethod authmethods[] = {
 	{"none",
 		userauth_none,
 		&one},
 	{"publickey",
 		userauth_pubkey,
 		&options.pubkey_authentication},
 	{"password",
 		userauth_passwd,
 		&options.password_authentication},
 	{"keyboard-interactive",
 		userauth_kbdint,
 		&options.kbd_interactive_authentication},
 	{"hostbased",
 		userauth_hostbased,
 		&options.hostbased_authentication},
 	{NULL, NULL, NULL}
 };

 /*
  * loop until authctxt->success == TRUE
  */

 Authctxt *
 do_authentication2(void)
 {
 	Authctxt *authctxt = authctxt_new();

 	x_authctxt = authctxt;		/*XXX*/

 	/* challenge-response is implemented via keyboard interactive */
 	if (options.challenge_response_authentication)
 		options.kbd_interactive_authentication = 1;
 	if (options.pam_authentication_via_kbd_int)
 		options.kbd_interactive_authentication = 1;

 	dispatch_init(&dispatch_protocol_error);
 	dispatch_set(SSH2_MSG_SERVICE_REQUEST, &input_service_request);
 	dispatch_run(DISPATCH_BLOCK, &authctxt->success, authctxt);

 	return (authctxt);
 }

 static void
 input_service_request(int type, u_int32_t seq, void *ctxt)
 {
 	Authctxt *authctxt = ctxt;
 	u_int len;
 	int accept = 0;
 	char *service = packet_get_string(&len);
 	packet_check_eom();

 	if (authctxt == NULL)
 		fatal("input_service_request: no authctxt");

 	if (strcmp(service, "ssh-userauth") == 0) {
 		if (!authctxt->success) {
 			accept = 1;
 			/* now we can handle user-auth requests */
 			dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &input_userauth_request);
 		}
 	}
 	/* XXX all other service requests are denied */

 	if (accept) {
 		packet_start(SSH2_MSG_SERVICE_ACCEPT);
 		packet_put_cstring(service);
 		packet_send();
 		packet_write_wait();
 	} else {
 		debug("bad service request %s", service);
 		packet_disconnect("bad service request %s", service);
 	}
 	xfree(service);
 }

 static void
 input_userauth_request(int type, u_int32_t seq, void *ctxt)
 {
 	Authctxt *authctxt = ctxt;
 	Authmethod *m = NULL;
 	char *user, *service, *method, *style = NULL;
 	int authenticated = 0;

 	if (authctxt == NULL)
 		fatal("input_userauth_request: no authctxt");

 	user = packet_get_string(NULL);
 	service = packet_get_string(NULL);
 	method = packet_get_string(NULL);
 	debug("userauth-request for user %s service %s method %s", user, service, method);
 	debug("attempt %d failures %d", authctxt->attempt, authctxt->failures);

 	if ((style = strchr(user, ':')) != NULL)
 		*style++ = 0;

 	if (authctxt->attempt++ == 0) {
 		/* setup auth context */
 		authctxt->pw = PRIVSEP(getpwnamallow(user));
 		if (authctxt->pw && strcmp(service, "ssh-connection")==0) {
 			authctxt->valid = 1;
 			debug2("input_userauth_request: setting up authctxt for %s", user);
 #ifdef USE_PAM
 			PRIVSEP(start_pam(authctxt->pw->pw_name));
 #endif
 		} else {
 			log("input_userauth_request: illegal user %s", user);
 #ifdef USE_PAM
 			PRIVSEP(start_pam("NOUSER"));
 #endif
 		}
 		setproctitle("%s%s", authctxt->pw ? user : "unknown",
 		    use_privsep ? " [net]" : "");
 		authctxt->user = xstrdup(user);
 		authctxt->service = xstrdup(service);
 		authctxt->style = style ? xstrdup(style) : NULL;
 		if (use_privsep)
 			mm_inform_authserv(service, style);
 	} else if (strcmp(user, authctxt->user) != 0 ||
 	    strcmp(service, authctxt->service) != 0) {
 		packet_disconnect("Change of username or service not allowed: "
 		    "(%s,%s) -> (%s,%s)",
 		    authctxt->user, authctxt->service, user, service);
 	}
 	/* reset state */
 	auth2_challenge_stop(authctxt);
 	authctxt->postponed = 0;

 	/* try to authenticate user */
 	m = authmethod_lookup(method);
 	if (m != NULL) {
 		debug2("input_userauth_request: try method %s", method);
 		authenticated =	m->userauth(authctxt);
 	}
 	userauth_finish(authctxt, authenticated, method);

 	xfree(service);
 	xfree(user);
 	xfree(method);
 }

 void
 userauth_finish(Authctxt *authctxt, int authenticated, char *method)
 {
 	char *methods;

 	if (!authctxt->valid && authenticated)
 		fatal("INTERNAL ERROR: authenticated invalid user %s",
 		    authctxt->user);

 	/* Special handling for root */
 	if (authenticated && authctxt->pw->pw_uid == 0 &&
 	    !auth_root_allowed(method))
 		authenticated = 0;

 #ifdef USE_PAM
 	if (!use_privsep && authenticated && authctxt->user &&
 	    !do_pam_account(authctxt->user, NULL))
 		authenticated = 0;
 #endif /* USE_PAM */

 	/* Log before sending the reply */
 	auth_log(authctxt, authenticated, method, " ssh2");

 	if (authctxt->postponed)
 		return;

 	/* XXX todo: check if multiple auth methods are needed */
 	if (authenticated == 1) {
 		/* turn off userauth */
 		dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &dispatch_protocol_ignore);
 		packet_start(SSH2_MSG_USERAUTH_SUCCESS);
 		packet_send();
 		packet_write_wait();
 		/* now we can break out */
 		authctxt->success = 1;
 	} else {
 		if (authctxt->failures++ > AUTH_FAIL_MAX) {
 #ifdef WITH_AIXAUTHENTICATE
 			loginfailed(authctxt->user,
 			    get_canonical_hostname(options.verify_reverse_mapping),
 			    "ssh");
 #endif /* WITH_AIXAUTHENTICATE */
 			packet_disconnect(AUTH_FAIL_MSG, authctxt->user);
 		}
 		methods = authmethods_get();
 		packet_start(SSH2_MSG_USERAUTH_FAILURE);
 		packet_put_cstring(methods);
 		packet_put_char(0);	/* XXX partial success, unused */
 		packet_send();
 		packet_write_wait();
 		xfree(methods);
 	}
 }

 static void
 userauth_banner(void)
 {
 	struct stat st;
 	char *banner = NULL;
 	off_t len, n;
 	int fd;

 	if (options.banner == NULL || (datafellows & SSH_BUG_BANNER))
 		return;
 	if ((fd = open(options.banner, O_RDONLY)) < 0)
 		return;
 	if (fstat(fd, &st) < 0)
 		goto done;
 	len = st.st_size;
 	banner = xmalloc(len + 1);
 	if ((n = read(fd, banner, len)) < 0)
 		goto done;
 	banner[n] = '\0';
 	packet_start(SSH2_MSG_USERAUTH_BANNER);
 	packet_put_cstring(banner);
 	packet_put_cstring("");		/* language, unused */
 	packet_send();
 	debug("userauth_banner: sent");
 done:
 	if (banner)
 		xfree(banner);
 	close(fd);
 	return;
 }

 static int
 userauth_none(Authctxt *authctxt)
 {
 	/* disable method "none", only allowed one time */
 	Authmethod *m = authmethod_lookup("none");
 	if (m != NULL)
 		m->enabled = NULL;
 	packet_check_eom();
 	userauth_banner();

 	if (authctxt->valid == 0)
 		return(0);

 #ifdef HAVE_CYGWIN
 	if (check_nt_auth(1, authctxt->pw) == 0)
 		return(0);
 #endif
 	return PRIVSEP(auth_password(authctxt, ""));
 }

 static int
 userauth_passwd(Authctxt *authctxt)
 {
 	char *password;
 	int authenticated = 0;
 	int change;
 	u_int len;
 	change = packet_get_char();
 	if (change)
 		log("password change not supported");
 	password = packet_get_string(&len);
 	packet_check_eom();
 	if (authctxt->valid &&
 #ifdef HAVE_CYGWIN
 	    check_nt_auth(1, authctxt->pw) &&
 #endif
 	    PRIVSEP(auth_password(authctxt, password)) == 1)
 		authenticated = 1;
 	memset(password, 0, len);
 	xfree(password);
 	return authenticated;
 }

 static int
 userauth_kbdint(Authctxt *authctxt)
 {
 	int authenticated = 0;
 	char *lang, *devs;

 	lang = packet_get_string(NULL);
 	devs = packet_get_string(NULL);
 	packet_check_eom();

 	debug("keyboard-interactive devs %s", devs);

 	if (options.challenge_response_authentication)
 		authenticated = auth2_challenge(authctxt, devs);

 #ifdef USE_PAM
 	if (authenticated == 0 && options.pam_authentication_via_kbd_int)
 		authenticated = auth2_pam(authctxt);
 #endif
 	xfree(devs);
 	xfree(lang);
 #ifdef HAVE_CYGWIN
 	if (check_nt_auth(0, authctxt->pw) == 0)
 		return(0);
 #endif
 	return authenticated;
 }

 static int
 userauth_pubkey(Authctxt *authctxt)
 {
 	Buffer b;
 	Key *key = NULL;
 	char *pkalg;
 	u_char *pkblob, *sig;
 	u_int alen, blen, slen;
 	int have_sig, pktype;
 	int authenticated = 0;

 	if (!authctxt->valid) {
 		debug2("userauth_pubkey: disabled because of invalid user");
 		return 0;
 	}
 	have_sig = packet_get_char();
 	if (datafellows & SSH_BUG_PKAUTH) {
 		debug2("userauth_pubkey: SSH_BUG_PKAUTH");
 		/* no explicit pkalg given */
 		pkblob = packet_get_string(&blen);
 		buffer_init(&b);
 		buffer_append(&b, pkblob, blen);
 		/* so we have to extract the pkalg from the pkblob */
 		pkalg = buffer_get_string(&b, &alen);
 		buffer_free(&b);
 	} else {
 		pkalg = packet_get_string(&alen);
 		pkblob = packet_get_string(&blen);
 	}
 	pktype = key_type_from_name(pkalg);
 	if (pktype == KEY_UNSPEC) {
 		/* this is perfectly legal */
 		log("userauth_pubkey: unsupported public key algorithm: %s",
 		    pkalg);
 		goto done;
 	}
 	key = key_from_blob(pkblob, blen);
 	if (key == NULL) {
 		error("userauth_pubkey: cannot decode key: %s", pkalg);
 		goto done;
 	}
 	if (key->type != pktype) {
 		error("userauth_pubkey: type mismatch for decoded key "
 		    "(received %d, expected %d)", key->type, pktype);
 		goto done;
 	}
 	if (have_sig) {
 		sig = packet_get_string(&slen);
 		packet_check_eom();
 		buffer_init(&b);
 		if (datafellows & SSH_OLD_SESSIONID) {
 			buffer_append(&b, session_id2, session_id2_len);
 		} else {
 			buffer_put_string(&b, session_id2, session_id2_len);
 		}
 		/* reconstruct packet */
 		buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
 		buffer_put_cstring(&b, authctxt->user);
 		buffer_put_cstring(&b,
 		    datafellows & SSH_BUG_PKSERVICE ?
 		    "ssh-userauth" :
 		    authctxt->service);
 		if (datafellows & SSH_BUG_PKAUTH) {
 			buffer_put_char(&b, have_sig);
 		} else {
 			buffer_put_cstring(&b, "publickey");
 			buffer_put_char(&b, have_sig);
 			buffer_put_cstring(&b, pkalg);
 		}
 		buffer_put_string(&b, pkblob, blen);
 #ifdef DEBUG_PK
 		buffer_dump(&b);
 #endif
 		/* test for correct signature */
 		authenticated = 0;
 		if (PRIVSEP(user_key_allowed(authctxt->pw, key)) &&
 		    PRIVSEP(key_verify(key, sig, slen, buffer_ptr(&b),
 				buffer_len(&b))) == 1)
 			authenticated = 1;
 		buffer_clear(&b);
 		xfree(sig);
 	} else {
 		debug("test whether pkalg/pkblob are acceptable");
 		packet_check_eom();

 		/* XXX fake reply and always send PK_OK ? */
 		/*
 		 * XXX this allows testing whether a user is allowed
 		 * to login: if you happen to have a valid pubkey this
 		 * message is sent. the message is NEVER sent at all
 		 * if a user is not allowed to login. is this an
 		 * issue? -markus
 		 */
 		if (PRIVSEP(user_key_allowed(authctxt->pw, key))) {
 			packet_start(SSH2_MSG_USERAUTH_PK_OK);
 			packet_put_string(pkalg, alen);
 			packet_put_string(pkblob, blen);
 			packet_send();
 			packet_write_wait();
 			authctxt->postponed = 1;
 		}
 	}
 	if (authenticated != 1)
 		auth_clear_options();
 done:
 	debug2("userauth_pubkey: authenticated %d pkalg %s", authenticated, pkalg);
 	if (key != NULL)
 		key_free(key);
 	xfree(pkalg);
 	xfree(pkblob);
 #ifdef HAVE_CYGWIN
 	if (check_nt_auth(0, authctxt->pw) == 0)
 		return(0);
 #endif
 	return authenticated;
 }

 static int
 userauth_hostbased(Authctxt *authctxt)
 {
 	Buffer b;
 	Key *key = NULL;
 	char *pkalg, *cuser, *chost, *service;
 	u_char *pkblob, *sig;
 	u_int alen, blen, slen;
 	int pktype;
 	int authenticated = 0;

 	if (!authctxt->valid) {
 		debug2("userauth_hostbased: disabled because of invalid user");
 		return 0;
 	}
 	pkalg = packet_get_string(&alen);
 	pkblob = packet_get_string(&blen);
 	chost = packet_get_string(NULL);
 	cuser = packet_get_string(NULL);
 	sig = packet_get_string(&slen);

 	debug("userauth_hostbased: cuser %s chost %s pkalg %s slen %d",
 	    cuser, chost, pkalg, slen);
 #ifdef DEBUG_PK
 	debug("signature:");
 	buffer_init(&b);
 	buffer_append(&b, sig, slen);
 	buffer_dump(&b);
 	buffer_free(&b);
 #endif
 	pktype = key_type_from_name(pkalg);
 	if (pktype == KEY_UNSPEC) {
 		/* this is perfectly legal */
 		log("userauth_hostbased: unsupported "
 		    "public key algorithm: %s", pkalg);
 		goto done;
 	}
 	key = key_from_blob(pkblob, blen);
 	if (key == NULL) {
 		error("userauth_hostbased: cannot decode key: %s", pkalg);
 		goto done;
 	}
 	if (key->type != pktype) {
 		error("userauth_hostbased: type mismatch for decoded key "
 		    "(received %d, expected %d)", key->type, pktype);
 		goto done;
 	}
 	service = datafellows & SSH_BUG_HBSERVICE ? "ssh-userauth" :
 	    authctxt->service;
 	buffer_init(&b);
 	buffer_put_string(&b, session_id2, session_id2_len);
 	/* reconstruct packet */
 	buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
 	buffer_put_cstring(&b, authctxt->user);
 	buffer_put_cstring(&b, service);
 	buffer_put_cstring(&b, "hostbased");
 	buffer_put_string(&b, pkalg, alen);
 	buffer_put_string(&b, pkblob, blen);
 	buffer_put_cstring(&b, chost);
 	buffer_put_cstring(&b, cuser);
 #ifdef DEBUG_PK
 	buffer_dump(&b);
 #endif
 	/* test for allowed key and correct signature */
 	authenticated = 0;
 	if (PRIVSEP(hostbased_key_allowed(authctxt->pw, cuser, chost, key)) &&
 	    PRIVSEP(key_verify(key, sig, slen, buffer_ptr(&b),
 			buffer_len(&b))) == 1)
 		authenticated = 1;

 	buffer_clear(&b);
 done:
 	debug2("userauth_hostbased: authenticated %d", authenticated);
 	if (key != NULL)
 		key_free(key);
 	xfree(pkalg);
 	xfree(pkblob);
 	xfree(cuser);
 	xfree(chost);
 	xfree(sig);
 	return authenticated;
 }

 /* get current user */

 struct passwd*
 auth_get_user(void)
 {
 	return (x_authctxt != NULL && x_authctxt->valid) ? x_authctxt->pw : NULL;
 }

 #define	DELIM	","

 static char *
 authmethods_get(void)
 {
 	Authmethod *method = NULL;
 	Buffer b;
 	char *list;

 	buffer_init(&b);
 	for (method = authmethods; method->name != NULL; method++) {
 		if (strcmp(method->name, "none") == 0)
 			continue;
 		if (method->enabled != NULL && *(method->enabled) != 0) {
 			if (buffer_len(&b) > 0)
 				buffer_append(&b, ",", 1);
 			buffer_append(&b, method->name, strlen(method->name));
 		}
 	}
 	buffer_append(&b, "\0", 1);
 	list = xstrdup(buffer_ptr(&b));
 	buffer_free(&b);
 	return list;
 }

 static Authmethod *
 authmethod_lookup(const char *name)
 {
 	Authmethod *method = NULL;
 	if (name != NULL)
 		for (method = authmethods; method->name != NULL; method++)
 			if (method->enabled != NULL &&
 			    *(method->enabled) != 0 &&
 			    strcmp(name, method->name) == 0)
 				return method;
 	debug2("Unrecognized authentication method name: %s", name ? name : "NULL");
 	return NULL;
 }

 /* return 1 if user allows given key */
 static int
 user_key_allowed2(struct passwd *pw, Key *key, char *file)
 {
 	char line[8192];
 	int found_key = 0;
 	FILE *f;
 	u_long linenum = 0;
 	struct stat st;
 	Key *found;
 	char *fp;

 	if (pw == NULL)
 		return 0;

 	/* Temporarily use the user's uid. */
 	temporarily_use_uid(pw);

 	debug("trying public key file %s", file);

 	/* Fail quietly if file does not exist */
 	if (stat(file, &st) < 0) {
 		/* Restore the privileged uid. */
 		restore_uid();
 		return 0;
 	}
 	/* Open the file containing the authorized keys. */
 	f = fopen(file, "r");
 	if (!f) {
 		/* Restore the privileged uid. */
 		restore_uid();
 		return 0;
 	}
 	if (options.strict_modes &&
 	    secure_filename(f, file, pw, line, sizeof(line)) != 0) {
 		fclose(f);
 		log("Authentication refused: %s", line);
 		restore_uid();
 		return 0;
 	}

 	found_key = 0;
 	found = key_new(key->type);

 	while (fgets(line, sizeof(line), f)) {
 		char *cp, *options = NULL;
 		linenum++;
 		/* Skip leading whitespace, empty and comment lines. */
 		for (cp = line; *cp == ' ' || *cp == '\t'; cp++)
 			;
 		if (!*cp || *cp == '\n' || *cp == '#')
 			continue;

 		if (key_read(found, &cp) != 1) {
 			/* no key?  check if there are options for this key */
 			int quoted = 0;
 			debug2("user_key_allowed: check options: '%s'", cp);
 			options = cp;
 			for (; *cp && (quoted || (*cp != ' ' && *cp != '\t')); cp++) {
 				if (*cp == '\\' && cp[1] == '"')
 					cp++;	/* Skip both */
 				else if (*cp == '"')
 					quoted = !quoted;
 			}
 			/* Skip remaining whitespace. */
 			for (; *cp == ' ' || *cp == '\t'; cp++)
 				;
 			if (key_read(found, &cp) != 1) {
 				debug2("user_key_allowed: advance: '%s'", cp);
 				/* still no key?  advance to next line*/
 				continue;
 			}
 		}
 		if (key_equal(found, key) &&
 		    auth_parse_options(pw, options, file, linenum) == 1) {
 			found_key = 1;
 			debug("matching key found: file %s, line %lu",
 			    file, linenum);
 			fp = key_fingerprint(found, SSH_FP_MD5, SSH_FP_HEX);
 			verbose("Found matching %s key: %s",
 			    key_type(found), fp);
 			xfree(fp);
 			break;
 		}
 	}
 	restore_uid();
 	fclose(f);
 	key_free(found);
 	if (!found_key)
 		debug2("key not found");
 	return found_key;
 }

 /* check whether given key is in .ssh/authorized_keys* */
 int
 user_key_allowed(struct passwd *pw, Key *key)
 {
 	int success;
 	char *file;

 	file = authorized_keys_file(pw);
 	success = user_key_allowed2(pw, key, file);
 	xfree(file);
 	if (success)
 		return success;

 	/* try suffix "2" for backward compat, too */
 	file = authorized_keys_file2(pw);
 	success = user_key_allowed2(pw, key, file);
 	xfree(file);
 	return success;
 }

 /* return 1 if given hostkey is allowed */
 int
 hostbased_key_allowed(struct passwd *pw, const char *cuser, char *chost,
     Key *key)
 {
 	const char *resolvedname, *ipaddr, *lookup;
 	HostStatus host_status;
 	int len;

 	resolvedname = get_canonical_hostname(options.verify_reverse_mapping);
 	ipaddr = get_remote_ipaddr();

 	debug2("userauth_hostbased: chost %s resolvedname %s ipaddr %s",
 	    chost, resolvedname, ipaddr);

 	if (options.hostbased_uses_name_from_packet_only) {
 		if (auth_rhosts2(pw, cuser, chost, chost) == 0)
 			return 0;
 		lookup = chost;
 	} else {
 		if (((len = strlen(chost)) > 0) && chost[len - 1] == '.') {
 			debug2("stripping trailing dot from chost %s", chost);
 			chost[len - 1] = '\0';
 		}
 		if (strcasecmp(resolvedname, chost) != 0)
 			log("userauth_hostbased mismatch: "
 			    "client sends %s, but we resolve %s to %s",
 			    chost, ipaddr, resolvedname);
 		if (auth_rhosts2(pw, cuser, resolvedname, ipaddr) == 0)
 			return 0;
 		lookup = resolvedname;
 	}
 	debug2("userauth_hostbased: access allowed by auth_rhosts2");

 	host_status = check_key_in_hostfiles(pw, key, lookup,
 	    _PATH_SSH_SYSTEM_HOSTFILE,
 	    options.ignore_user_known_hosts ? NULL : _PATH_SSH_USER_HOSTFILE);

 	/* backward compat if no key has been found. */
 	if (host_status == HOST_NEW)
 		host_status = check_key_in_hostfiles(pw, key, lookup,
 		    _PATH_SSH_SYSTEM_HOSTFILE2,
 		    options.ignore_user_known_hosts ? NULL :
 		    _PATH_SSH_USER_HOSTFILE2);

 	return (host_status == HOST_OK);
 }
	/*
	* Copyright (c) 2000 Markus Friedl. All rights reserved.
	*
	* Redistribution and use in source and binary forms, with or without
	* modification, are permitted provided that the following conditions
	* are met:
	* 1. Redistributions of source code must retain the above copyright
	* notice, this list of conditions and the following disclaimer.
	* 2. Redistributions in binary form must reproduce the above copyright
	* notice, this list of conditions and the following disclaimer in the
	* documentation and/or other materials provided with the distribution.
	*
	* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
	* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
	* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
	* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
	* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
	* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
	* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
	* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
	* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
	* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
	*/

	#include "includes.h"
	RCSID("$OpenBSD: auth2.c,v 1.89 2002/03/19 14:27:39 markus Exp $");

	#include <openssl/evp.h>

	#include "ssh2.h"
	#include "xmalloc.h"
	#include "rsa.h"
	#include "sshpty.h"
	#include "packet.h"
	#include "buffer.h"
	#include "log.h"
	#include "servconf.h"
	#include "compat.h"
	#include "channels.h"
	#include "bufaux.h"
	#include "auth.h"
	#include "session.h"
	#include "dispatch.h"
	#include "key.h"
	#include "cipher.h"
	#include "kex.h"
	#include "pathnames.h"
	#include "uidswap.h"
	#include "auth-options.h"
	#include "hostfile.h"
	#include "canohost.h"
	#include "match.h"
	#include "monitor_wrap.h"

	/* import */
	extern ServerOptions options;
	extern u_char *session_id2;
	extern int session_id2_len;

	Authctxt *x_authctxt = NULL;
	static int one = 1;

	typedef struct Authmethod Authmethod;
	struct Authmethod {
	char *name;
	int (userauth)(Authctxt authctxt);
	int *enabled;
	};

	/* protocol */

	static void input_service_request(int, u_int32_t, void *);
	static void input_userauth_request(int, u_int32_t, void *);

	/* helper */
	static Authmethod authmethod_lookup(const char );
	static char *authmethods_get(void);
	int user_key_allowed(struct passwd , Key );
	int hostbased_key_allowed(struct passwd , const char , char , Key );

	/* auth */
	static void userauth_banner(void);
	static int userauth_none(Authctxt *);
	static int userauth_passwd(Authctxt *);
	static int userauth_pubkey(Authctxt *);
	static int userauth_hostbased(Authctxt *);
	static int userauth_kbdint(Authctxt *);

	Authmethod authmethods[] = {
	{"none",
	userauth_none,
	&one},
	{"publickey",
	userauth_pubkey,
	&options.pubkey_authentication},
	{"password",
	userauth_passwd,
	&options.password_authentication},
	{"keyboard-interactive",
	userauth_kbdint,
	&options.kbd_interactive_authentication},
	{"hostbased",
	userauth_hostbased,
	&options.hostbased_authentication},
	{NULL, NULL, NULL}
	};

	/*
	* loop until authctxt->success == TRUE
	*/

	Authctxt *
	do_authentication2(void)
	{
	Authctxt *authctxt = authctxt_new();

	x_authctxt = authctxt; /XXX/

	/* challenge-response is implemented via keyboard interactive */
	if (options.challenge_response_authentication)
	options.kbd_interactive_authentication = 1;
	if (options.pam_authentication_via_kbd_int)
	options.kbd_interactive_authentication = 1;

	dispatch_init(&dispatch_protocol_error);
	dispatch_set(SSH2_MSG_SERVICE_REQUEST, &input_service_request);
	dispatch_run(DISPATCH_BLOCK, &authctxt->success, authctxt);

	return (authctxt);
	}

	static void
	input_service_request(int type, u_int32_t seq, void *ctxt)
	{
	Authctxt *authctxt = ctxt;
	u_int len;
	int accept = 0;
	char *service = packet_get_string(&len);
	packet_check_eom();

	if (authctxt == NULL)
	fatal("input_service_request: no authctxt");

	if (strcmp(service, "ssh-userauth") == 0) {
	if (!authctxt->success) {
	accept = 1;
	/* now we can handle user-auth requests */
	dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &input_userauth_request);
	}
	}
	/* XXX all other service requests are denied */

	if (accept) {
	packet_start(SSH2_MSG_SERVICE_ACCEPT);
	packet_put_cstring(service);
	packet_send();
	packet_write_wait();
	} else {
	debug("bad service request %s", service);
	packet_disconnect("bad service request %s", service);
	}
	xfree(service);
	}

	static void
	input_userauth_request(int type, u_int32_t seq, void *ctxt)
	{
	Authctxt *authctxt = ctxt;
	Authmethod *m = NULL;
	char user, service, method, style = NULL;
	int authenticated = 0;

	if (authctxt == NULL)
	fatal("input_userauth_request: no authctxt");

	user = packet_get_string(NULL);
	service = packet_get_string(NULL);
	method = packet_get_string(NULL);
	debug("userauth-request for user %s service %s method %s", user, service, method);
	debug("attempt %d failures %d", authctxt->attempt, authctxt->failures);

	if ((style = strchr(user, ':')) != NULL)
	*style++ = 0;

	if (authctxt->attempt++ == 0) {
	/* setup auth context */
	authctxt->pw = PRIVSEP(getpwnamallow(user));
	if (authctxt->pw && strcmp(service, "ssh-connection")==0) {
	authctxt->valid = 1;
	debug2("input_userauth_request: setting up authctxt for %s", user);
	#ifdef USE_PAM
	PRIVSEP(start_pam(authctxt->pw->pw_name));
	#endif
	} else {
	log("input_userauth_request: illegal user %s", user);
	#ifdef USE_PAM
	PRIVSEP(start_pam("NOUSER"));
	#endif
	}
	setproctitle("%s%s", authctxt->pw ? user : "unknown",
	use_privsep ? " [net]" : "");
	authctxt->user = xstrdup(user);
	authctxt->service = xstrdup(service);
	authctxt->style = style ? xstrdup(style) : NULL;
	if (use_privsep)
	mm_inform_authserv(service, style);
	} else if (strcmp(user, authctxt->user) != 0 \|\|
	strcmp(service, authctxt->service) != 0) {
	packet_disconnect("Change of username or service not allowed: "
	"(%s,%s) -> (%s,%s)",
	authctxt->user, authctxt->service, user, service);
	}
	/* reset state */
	auth2_challenge_stop(authctxt);
	authctxt->postponed = 0;

	/* try to authenticate user */
	m = authmethod_lookup(method);
	if (m != NULL) {
	debug2("input_userauth_request: try method %s", method);
	authenticated = m->userauth(authctxt);
	}
	userauth_finish(authctxt, authenticated, method);

	xfree(service);
	xfree(user);
	xfree(method);
	}

	void
	userauth_finish(Authctxt authctxt, int authenticated, char method)
	{
	char *methods;

	if (!authctxt->valid && authenticated)
	fatal("INTERNAL ERROR: authenticated invalid user %s",
	authctxt->user);

	/* Special handling for root */
	if (authenticated && authctxt->pw->pw_uid == 0 &&
	!auth_root_allowed(method))
	authenticated = 0;

	#ifdef USE_PAM
	if (!use_privsep && authenticated && authctxt->user &&
	!do_pam_account(authctxt->user, NULL))
	authenticated = 0;
	#endif /* USE_PAM */

	/* Log before sending the reply */
	auth_log(authctxt, authenticated, method, " ssh2");

	if (authctxt->postponed)
	return;

	/* XXX todo: check if multiple auth methods are needed */
	if (authenticated == 1) {
	/* turn off userauth */
	dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &dispatch_protocol_ignore);
	packet_start(SSH2_MSG_USERAUTH_SUCCESS);
	packet_send();
	packet_write_wait();
	/* now we can break out */
	authctxt->success = 1;
	} else {
	if (authctxt->failures++ > AUTH_FAIL_MAX) {
	#ifdef WITH_AIXAUTHENTICATE
	loginfailed(authctxt->user,
	get_canonical_hostname(options.verify_reverse_mapping),
	"ssh");
	#endif /* WITH_AIXAUTHENTICATE */
	packet_disconnect(AUTH_FAIL_MSG, authctxt->user);
	}
	methods = authmethods_get();
	packet_start(SSH2_MSG_USERAUTH_FAILURE);
	packet_put_cstring(methods);
	packet_put_char(0); /* XXX partial success, unused */
	packet_send();
	packet_write_wait();
	xfree(methods);
	}
	}

	static void
	userauth_banner(void)
	{
	struct stat st;
	char *banner = NULL;
	off_t len, n;
	int fd;

	if (options.banner == NULL \|\| (datafellows & SSH_BUG_BANNER))
	return;
	if ((fd = open(options.banner, O_RDONLY)) < 0)
	return;
	if (fstat(fd, &st) < 0)
	goto done;
	len = st.st_size;
	banner = xmalloc(len + 1);
	if ((n = read(fd, banner, len)) < 0)
	goto done;
	banner[n] = '\0';
	packet_start(SSH2_MSG_USERAUTH_BANNER);
	packet_put_cstring(banner);
	packet_put_cstring(""); /* language, unused */
	packet_send();
	debug("userauth_banner: sent");
	done:
	if (banner)
	xfree(banner);
	close(fd);
	return;
	}

	static int
	userauth_none(Authctxt *authctxt)
	{
	/* disable method "none", only allowed one time */
	Authmethod *m = authmethod_lookup("none");
	if (m != NULL)
	m->enabled = NULL;
	packet_check_eom();
	userauth_banner();

	if (authctxt->valid == 0)
	return(0);

	#ifdef HAVE_CYGWIN
	if (check_nt_auth(1, authctxt->pw) == 0)
	return(0);
	#endif
	return PRIVSEP(auth_password(authctxt, ""));
	}

	static int
	userauth_passwd(Authctxt *authctxt)
	{
	char *password;
	int authenticated = 0;
	int change;
	u_int len;
	change = packet_get_char();
	if (change)
	log("password change not supported");
	password = packet_get_string(&len);
	packet_check_eom();
	if (authctxt->valid &&
	#ifdef HAVE_CYGWIN
	check_nt_auth(1, authctxt->pw) &&
	#endif
	PRIVSEP(auth_password(authctxt, password)) == 1)
	authenticated = 1;
	memset(password, 0, len);
	xfree(password);
	return authenticated;
	}

	static int
	userauth_kbdint(Authctxt *authctxt)
	{
	int authenticated = 0;
	char lang, devs;

	lang = packet_get_string(NULL);
	devs = packet_get_string(NULL);
	packet_check_eom();

	debug("keyboard-interactive devs %s", devs);

	if (options.challenge_response_authentication)
	authenticated = auth2_challenge(authctxt, devs);

	#ifdef USE_PAM
	if (authenticated == 0 && options.pam_authentication_via_kbd_int)
	authenticated = auth2_pam(authctxt);
	#endif
	xfree(devs);
	xfree(lang);
	#ifdef HAVE_CYGWIN
	if (check_nt_auth(0, authctxt->pw) == 0)
	return(0);
	#endif
	return authenticated;
	}

	static int
	userauth_pubkey(Authctxt *authctxt)
	{
	Buffer b;
	Key *key = NULL;
	char *pkalg;
	u_char pkblob, sig;
	u_int alen, blen, slen;
	int have_sig, pktype;
	int authenticated = 0;

	if (!authctxt->valid) {
	debug2("userauth_pubkey: disabled because of invalid user");
	return 0;
	}
	have_sig = packet_get_char();
	if (datafellows & SSH_BUG_PKAUTH) {
	debug2("userauth_pubkey: SSH_BUG_PKAUTH");
	/* no explicit pkalg given */
	pkblob = packet_get_string(&blen);
	buffer_init(&b);
	buffer_append(&b, pkblob, blen);
	/* so we have to extract the pkalg from the pkblob */
	pkalg = buffer_get_string(&b, &alen);
	buffer_free(&b);
	} else {
	pkalg = packet_get_string(&alen);
	pkblob = packet_get_string(&blen);
	}
	pktype = key_type_from_name(pkalg);
	if (pktype == KEY_UNSPEC) {
	/* this is perfectly legal */
	log("userauth_pubkey: unsupported public key algorithm: %s",
	pkalg);
	goto done;
	}
	key = key_from_blob(pkblob, blen);
	if (key == NULL) {
	error("userauth_pubkey: cannot decode key: %s", pkalg);
	goto done;
	}
	if (key->type != pktype) {
	error("userauth_pubkey: type mismatch for decoded key "
	"(received %d, expected %d)", key->type, pktype);
	goto done;
	}
	if (have_sig) {
	sig = packet_get_string(&slen);
	packet_check_eom();
	buffer_init(&b);
	if (datafellows & SSH_OLD_SESSIONID) {
	buffer_append(&b, session_id2, session_id2_len);
	} else {
	buffer_put_string(&b, session_id2, session_id2_len);
	}
	/* reconstruct packet */
	buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
	buffer_put_cstring(&b, authctxt->user);
	buffer_put_cstring(&b,
	datafellows & SSH_BUG_PKSERVICE ?
	"ssh-userauth" :
	authctxt->service);
	if (datafellows & SSH_BUG_PKAUTH) {
	buffer_put_char(&b, have_sig);
	} else {
	buffer_put_cstring(&b, "publickey");
	buffer_put_char(&b, have_sig);
	buffer_put_cstring(&b, pkalg);
	}
	buffer_put_string(&b, pkblob, blen);
	#ifdef DEBUG_PK
	buffer_dump(&b);
	#endif
	/* test for correct signature */
	authenticated = 0;
	if (PRIVSEP(user_key_allowed(authctxt->pw, key)) &&
	PRIVSEP(key_verify(key, sig, slen, buffer_ptr(&b),
	buffer_len(&b))) == 1)
	authenticated = 1;
	buffer_clear(&b);
	xfree(sig);
	} else {
	debug("test whether pkalg/pkblob are acceptable");
	packet_check_eom();

	/* XXX fake reply and always send PK_OK ? */
	/*
	* XXX this allows testing whether a user is allowed
	* to login: if you happen to have a valid pubkey this
	* message is sent. the message is NEVER sent at all
	* if a user is not allowed to login. is this an
	* issue? -markus
	*/
	if (PRIVSEP(user_key_allowed(authctxt->pw, key))) {
	packet_start(SSH2_MSG_USERAUTH_PK_OK);
	packet_put_string(pkalg, alen);
	packet_put_string(pkblob, blen);
	packet_send();
	packet_write_wait();
	authctxt->postponed = 1;
	}
	}
	if (authenticated != 1)
	auth_clear_options();
	done:
	debug2("userauth_pubkey: authenticated %d pkalg %s", authenticated, pkalg);
	if (key != NULL)
	key_free(key);
	xfree(pkalg);
	xfree(pkblob);
	#ifdef HAVE_CYGWIN
	if (check_nt_auth(0, authctxt->pw) == 0)
	return(0);
	#endif
	return authenticated;
	}

	static int
	userauth_hostbased(Authctxt *authctxt)
	{
	Buffer b;
	Key *key = NULL;
	char pkalg, cuser, chost, service;
	u_char pkblob, sig;
	u_int alen, blen, slen;
	int pktype;
	int authenticated = 0;

	if (!authctxt->valid) {
	debug2("userauth_hostbased: disabled because of invalid user");
	return 0;
	}
	pkalg = packet_get_string(&alen);
	pkblob = packet_get_string(&blen);
	chost = packet_get_string(NULL);
	cuser = packet_get_string(NULL);
	sig = packet_get_string(&slen);

	debug("userauth_hostbased: cuser %s chost %s pkalg %s slen %d",
	cuser, chost, pkalg, slen);
	#ifdef DEBUG_PK
	debug("signature:");
	buffer_init(&b);
	buffer_append(&b, sig, slen);
	buffer_dump(&b);
	buffer_free(&b);
	#endif
	pktype = key_type_from_name(pkalg);
	if (pktype == KEY_UNSPEC) {
	/* this is perfectly legal */
	log("userauth_hostbased: unsupported "
	"public key algorithm: %s", pkalg);
	goto done;
	}
	key = key_from_blob(pkblob, blen);
	if (key == NULL) {
	error("userauth_hostbased: cannot decode key: %s", pkalg);
	goto done;
	}
	if (key->type != pktype) {
	error("userauth_hostbased: type mismatch for decoded key "
	"(received %d, expected %d)", key->type, pktype);
	goto done;
	}
	service = datafellows & SSH_BUG_HBSERVICE ? "ssh-userauth" :
	authctxt->service;
	buffer_init(&b);
	buffer_put_string(&b, session_id2, session_id2_len);
	/* reconstruct packet */
	buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
	buffer_put_cstring(&b, authctxt->user);
	buffer_put_cstring(&b, service);
	buffer_put_cstring(&b, "hostbased");
	buffer_put_string(&b, pkalg, alen);
	buffer_put_string(&b, pkblob, blen);
	buffer_put_cstring(&b, chost);
	buffer_put_cstring(&b, cuser);
	#ifdef DEBUG_PK
	buffer_dump(&b);
	#endif
	/* test for allowed key and correct signature */
	authenticated = 0;
	if (PRIVSEP(hostbased_key_allowed(authctxt->pw, cuser, chost, key)) &&
	PRIVSEP(key_verify(key, sig, slen, buffer_ptr(&b),
	buffer_len(&b))) == 1)
	authenticated = 1;

	buffer_clear(&b);
	done:
	debug2("userauth_hostbased: authenticated %d", authenticated);
	if (key != NULL)
	key_free(key);
	xfree(pkalg);
	xfree(pkblob);
	xfree(cuser);
	xfree(chost);
	xfree(sig);
	return authenticated;
	}

	/* get current user */

	struct passwd*
	auth_get_user(void)
	{
	return (x_authctxt != NULL && x_authctxt->valid) ? x_authctxt->pw : NULL;
	}

	#define DELIM ","

	static char *
	authmethods_get(void)
	{
	Authmethod *method = NULL;
	Buffer b;
	char *list;

	buffer_init(&b);
	for (method = authmethods; method->name != NULL; method++) {
	if (strcmp(method->name, "none") == 0)
	continue;
	if (method->enabled != NULL && *(method->enabled) != 0) {
	if (buffer_len(&b) > 0)
	buffer_append(&b, ",", 1);
	buffer_append(&b, method->name, strlen(method->name));
	}
	}
	buffer_append(&b, "\0", 1);
	list = xstrdup(buffer_ptr(&b));
	buffer_free(&b);
	return list;
	}

	static Authmethod *
	authmethod_lookup(const char *name)
	{
	Authmethod *method = NULL;
	if (name != NULL)
	for (method = authmethods; method->name != NULL; method++)
	if (method->enabled != NULL &&
	*(method->enabled) != 0 &&
	strcmp(name, method->name) == 0)
	return method;
	debug2("Unrecognized authentication method name: %s", name ? name : "NULL");
	return NULL;
	}

	/* return 1 if user allows given key */
	static int
	user_key_allowed2(struct passwd pw, Key key, char *file)
	{
	char line[8192];
	int found_key = 0;
	FILE *f;
	u_long linenum = 0;
	struct stat st;
	Key *found;
	char *fp;

	if (pw == NULL)
	return 0;

	/* Temporarily use the user's uid. */
	temporarily_use_uid(pw);

	debug("trying public key file %s", file);

	/* Fail quietly if file does not exist */
	if (stat(file, &st) < 0) {
	/* Restore the privileged uid. */
	restore_uid();
	return 0;
	}
	/* Open the file containing the authorized keys. */
	f = fopen(file, "r");
	if (!f) {
	/* Restore the privileged uid. */
	restore_uid();
	return 0;
	}
	if (options.strict_modes &&
	secure_filename(f, file, pw, line, sizeof(line)) != 0) {
	fclose(f);
	log("Authentication refused: %s", line);
	restore_uid();
	return 0;
	}

	found_key = 0;
	found = key_new(key->type);

	while (fgets(line, sizeof(line), f)) {
	char cp, options = NULL;
	linenum++;
	/* Skip leading whitespace, empty and comment lines. */
	for (cp = line; cp == ' ' \|\| cp == '\t'; cp++)
	;
	if (!cp \|\| cp == '\n' \|\| *cp == '#')
	continue;

	if (key_read(found, &cp) != 1) {
	/* no key? check if there are options for this key */
	int quoted = 0;
	debug2("user_key_allowed: check options: '%s'", cp);
	options = cp;
	for (; cp && (quoted \|\| (cp != ' ' && *cp != '\t')); cp++) {
	if (*cp == '\\' && cp[1] == '"')
	cp++; /* Skip both */
	else if (*cp == '"')
	quoted = !quoted;
	}
	/* Skip remaining whitespace. */
	for (; cp == ' ' \|\| cp == '\t'; cp++)
	;
	if (key_read(found, &cp) != 1) {
	debug2("user_key_allowed: advance: '%s'", cp);
	/* still no key? advance to next line*/
	continue;
	}
	}
	if (key_equal(found, key) &&
	auth_parse_options(pw, options, file, linenum) == 1) {
	found_key = 1;
	debug("matching key found: file %s, line %lu",
	file, linenum);
	fp = key_fingerprint(found, SSH_FP_MD5, SSH_FP_HEX);
	verbose("Found matching %s key: %s",
	key_type(found), fp);
	xfree(fp);
	break;
	}
	}
	restore_uid();
	fclose(f);
	key_free(found);
	if (!found_key)
	debug2("key not found");
	return found_key;
	}

	/* check whether given key is in .ssh/authorized_keys* */
	int
	user_key_allowed(struct passwd pw, Key key)
	{
	int success;
	char *file;

	file = authorized_keys_file(pw);
	success = user_key_allowed2(pw, key, file);
	xfree(file);
	if (success)
	return success;

	/* try suffix "2" for backward compat, too */
	file = authorized_keys_file2(pw);
	success = user_key_allowed2(pw, key, file);
	xfree(file);
	return success;
	}

	/* return 1 if given hostkey is allowed */
	int
	hostbased_key_allowed(struct passwd pw, const char cuser, char *chost,
	Key *key)
	{
	const char resolvedname, ipaddr, *lookup;
	HostStatus host_status;
	int len;

	resolvedname = get_canonical_hostname(options.verify_reverse_mapping);
	ipaddr = get_remote_ipaddr();

	debug2("userauth_hostbased: chost %s resolvedname %s ipaddr %s",
	chost, resolvedname, ipaddr);

	if (options.hostbased_uses_name_from_packet_only) {
	if (auth_rhosts2(pw, cuser, chost, chost) == 0)
	return 0;
	lookup = chost;
	} else {
	if (((len = strlen(chost)) > 0) && chost[len - 1] == '.') {
	debug2("stripping trailing dot from chost %s", chost);
	chost[len - 1] = '\0';
	}
	if (strcasecmp(resolvedname, chost) != 0)
	log("userauth_hostbased mismatch: "
	"client sends %s, but we resolve %s to %s",
	chost, ipaddr, resolvedname);
	if (auth_rhosts2(pw, cuser, resolvedname, ipaddr) == 0)
	return 0;
	lookup = resolvedname;
	}
	debug2("userauth_hostbased: access allowed by auth_rhosts2");

	host_status = check_key_in_hostfiles(pw, key, lookup,
	_PATH_SSH_SYSTEM_HOSTFILE,
	options.ignore_user_known_hosts ? NULL : _PATH_SSH_USER_HOSTFILE);

	/* backward compat if no key has been found. */
	if (host_status == HOST_NEW)
	host_status = check_key_in_hostfiles(pw, key, lookup,
	_PATH_SSH_SYSTEM_HOSTFILE2,
	options.ignore_user_known_hosts ? NULL :
	_PATH_SSH_USER_HOSTFILE2);

	return (host_status == HOST_OK);
	}